Water droplet size

Effect of Physical Properties on Drop Size Because of the extreme variety of available geometries, no attempt to encompass this variable is made here. The suggested predictive route starts with air-water droplet size data from the manulac turer at the chosen flow rate. This drop size is then corrected by Eq. (14-195) for different viscosity and surface tension ... 

SMD = U— COrpsd Derived from water droplet size measurements No liquid properties included Applicable only to water Oyama Endou [472]... 

The emulsification state of water in butter (i.e. the water droplet size) is very important for the quality of the product. Bacteria in butter can grow only in the aqueous emulsified phase. A finely divided aqueous phase restricts bacterial growth since the nutrients available in small droplets will quickly become limiting. Also, unless bacterial contamination is high, it is likely that most small water droplets in butter are sterile. 

Water droplet size In oil. It is difficult to predict the water droplet lize that must be settled out of the oil phase to coincide with the rather loose definition of free oil. Unless laboratory or nearby field data is available, size the oil pad so... 

Water droplet size. The one thing remaining to be determined before developing a design procedure is the water droplet size to be used in the settling equation It is e.x-... 

Additional field data show that the low dilution water use rates can be maintained and still meet the required mixing efficiencies. The problem encountered with very low BS W contents is produced water droplet size and their disperaement in oil When 99.9% of the produced water has been removed, the remaining 0.1% consists of thousands of very small droplets more or less evenly distributed throughout the oil. To... 

The skimming units are divided into parallel channels and designed so that an oil droplet 150 g. or larger will be separated from the water. Droplet size is based on the oil droplet rise rate being equal to or greater than the overflow rate (Overflow rate = throughput t effective surface area.)... 

Fleisher et al. [12] studied the self-diffusion of oil and water in rape seeds. The selfdiffusion of oil was found to be completely restricted. The experiments could be explained in toms of the model of diffusion within spherical droplets and a Gaussian mass distribution of the droplet radii. At the same time Van den Enden et al. [9] introduced the technique described above. It is a rapid method for the determination of water droplet size distributions in spreads by using low resolution pulsed field gradient NMR. Their method was based on the recognition that a set of echo attenuation values (R) as a function of the field gradient pulsed width, obtained under conditions where R is independent of the time allowed for diffusion, contains all the necessary information on the water droplet size distribution (see above). A log-normal distribution of water droplet sizes was assumed. 

The pulsed field gradient NMR technique can be readily used for the determination of the water droplet size distribution in W/O emulsions or the oil droplet size distributions in O/W emulsions. Important advantages are the non-invasive nature, the ease of sample preparation, and the feet that pulsed field gradient NMR measures the droplet size distribution of the bulk in contrast with microscopic methods which estimate the size distribution of the surface. Both the proposed matrix method and the iterative curve fitting procedure can be successfully applied in a factory environment. The method can be implemented on a high as well as on a low resolution NMR spectrometer. 

The water phase is emulsified within the oil phase. Usually the oil phase fraction is much greater than the water phase fraction, so the large majority of oil production involves a water within oil (W/O) emulsion. The water droplet size is typically tens of microns (p,m). 

Arnold, K. E., and Thro, M. E., Water-Droplet-Size Determination for Improved Oil-Treater Sizing , SPE Technical Paper No. SPE 28537, Society of Petroleum Engineers Conference, New Orleans, LA, May 1997. 

The process line for this purpose is normally especially designed to ensure crystallization and texturization of the product to take place under controlled conditions and within the processing equipment. The manufacmre under high degree of agitation with minimal shear precedes the processing of the emulsion, providing an emulsion of the correct phase (water-oil) and water droplet size. 

Milk proteins and soy lecithin can also affect the water droplet size. Proteins and lecithin tend to increase the drop size (91, 100). 

A method requiring much less mechanical energy uses phase inversion see also the discussion of phase inversion temperature in the section Emulsifying Agents )- For example, if ultimately a W/O emulsion is desired, then a coarse OAV emulsion is first prepared by the addition of mechanical energy, and the oil content is progressively increased. At some volume fraction above 60-70%, the emulsion will suddenly invert and produce a W/O emulsion of much smaller water droplet sizes than were the oil droplets in the original O/W emulsion. 

A portion of the water in an emulsion can be dispersed within the oil droplets. This portion of the total water should be treated as oil when estimating emulsion viscosity. Generally, added water is present in the continuous phase. If the crude oil contains water prior to emulsion formation, this water may be present in either the continuous (water) phase or the dispersed (oil) phase after emulsion formation, depending primarily on the water droplet size in the crude oil. In order to predict how much of the water in the crude oil will be freed into the continuous phase, emulsion preparation experiments with the actual crude oil to be used are necessary. 

Water Droplet Size. To find a solution to the settling equation (i.e., for either equation 1 or 2), the water droplet size, d, must be known. Qualitatively, the water droplet size is expected to increase with an increase in retention time in the coalescing section and with heat input. Conversely, it should decrease with increase in the oil-phase viscosity. Furthermore, viscosity will have a greater effect on coalescence than temperature. Practical experience in the design of treaters has resulted in a reliable correlation of water droplet size to oil-phase viscosity (3) ... 

Balinov, B., Soderman, O., and Warnheim, T. Determination of water droplet sizes in margarines and low-calorie spreads by means of the NMR self-diffusion experiment, /. Am. Oil Chem. Soc., 71, 513, 1994. 

Fourel, L, Guillement, J.P., and Le Botlan, D. Determination of water droplet size distributions by low resolution PFG-NMR, /. Colloid Interface Sci, 169,119,1995. 

The total range of water droplet sizes observed in the froth samples was larger than suggested in Table III. Whereas the mean droplet sizes were consistently in the range 600—800 pm, some droplets as large as 1400 m and as small as <100 /zm were observed. That the smaller size droplets were observed qualitatively corresponds with the measurements made by Chung et al. (66) for emulsified water droplets that were up to about 18 pm. The larger droplets determined in the present work presumably correspond to the free water phase. 

Dedicated benchtop NMR analyzers for a variety of applications are available. Broker s Minispec mq series (www.minispec.com) includes an analyzer to determine fluoride in toothpaste quantitatively and another to determine water droplet size distribution in oil/water emulsions. Fluoride is often added to toothpaste as sodium fluoride or sodium monofluorophosphate to prevent tooth decay. The fluorine analyzer can determine fluorine and hydrogen at the level of a few hundred ppm. Toothpaste is squeezed into a glass sample tube and the quantitative determination of fluorine takes less than 1 min. The NMR method uses no solvents or reagents and is independent of the sample color... 

The diffusion studies described in the above sections pertain to water-continuous and bicontinuous microemulsions. Chen and Georges [34] were the first to study diffusion in oil-continuous microemulsions using steady-state microelectrode voltammetry. Ferrocene was used to probe diffusion in an SDS-dodecane-1-heptanol-water system. The diffusion coefficient of the hydrophobic probe indicated the microviscosity of the oil rather than the bulk viscosity of the microemulsion. Owlia et al. [36] reported diffusion coefficient measurements of water droplets in an Aerosol OT [AOT, bis(2-ethylhexyl)sulfosuccinate] microemulsion using a microelectrode. Water-soluble cobalt(II) corrin complex (vitamin Bi2r) was used in an oil-continuous microemulsion containing 0.2 M AOT, 4 M water buffered at pH 3, and isooctane. The apparent diffusion coefficient decreased with the probe concentration in accordance with Eq. (13) as shown in Fig. 6 [36]. The water droplet size was... 

The original emulsion is an oil/water (OAV) emulsion with a eomposition (in pereentage) of water/oil/ surfactant (W-O-S) 54-40-6. The surfaetant is Tween 80, a water-soluble surfaetant, and the oil is soybean oil, a liquid triglyceride. This is the simplest case of an emulsion, and the evaporation should in prineiple consist of the amount of water being redueed eausing an inversion from the original 0/W emulsion to a W/0 emulsion, followed by a slow reduction of the water droplet size and a final disappearance of them to leave an oil phase. 

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